Iodide-iodine etching solutions have been employed to recover precious metals from ore and scrap materials and have since been employed in the electronic and jewelry making industries in the etching and stripping of precious metals. Use of iodide-iodine solutions avoid toxicity problems associated with the previously used cyanide etching solutions but are considered costly.
Methods to reclaim spent iodide-iodine etching solutions have been developed to decrease the costs associated with their use. U.S. Pat. No. 3,957,505 discloses a process that dissolves and precipitates gold in potassium iodide-iodine using a reducing agent and a buffer. The solution can then be regenerated through the use of an oxidizing agent. U.S. Pat. No. 5,137,700 discloses the use of a hydroidic acid and iodine solution or ammonium iodide and iodine solution for the recovery of precious metals. A reducing agent is added to the solution with a buffer and the precious metal is precipitated from the solution. The spent solution is then treated to either oxidize it to its original state or to precipitate out the elemental iodine which is then used to supply the components for a new etching solution.